1. Field of the Invention
The present invention relates to a method for producing an oxide confined semiconductor laser that involves a vertical-cavity surface emitting laser (VCSEL) technology and its manufacturing process, and more particularly to a vertical-cavity surface emitting laser device and its manufacturing method that directly construct a light emitting active area and a wire bonding area on the structure of a semiconductor material by a dual platform method.
2. Description of Prior Art
Optical information and communication systems provide a major method for moving huge data in a high speed, and one of the main components of such optical information and communication systems is an optical transceiver. At the data transmitting end, an optical transceiver is provided for translating a data in the form of electric signals (such as a digital data in the form of 0 and 1) into an optical signal which is suitable to be transmitted by a transmission medium (such as an optical fiber cable). At the data receiving end, the optical transceiver translates the received optical signal back into a data in the form of electric signals. One of the major components of the foregoing optical transmitter is an optical transmitter for transmitting optical data, and typical optical transmitters for the preferred embodiment are light emitting diode (LED) and semiconductor laser diode (LASER), wherein the semiconductor laser diode (LASER) has a higher transmission speed, and thus becoming the subject for main development and applications of the present optical communication system.
Most of the present optical transmitters used for optical information communication systems are surface emitting semiconductor laser diode (LASER) such as the vertical-cavity surface emitting laser (VCSEL). As its name suggests, the laser beam is emitted vertically from the surface of the component, characterized in that the upper and lower Distributed Bragg Reflectors (DBR) are used to define a laser cavity. Unlike the edge emitting laser, the surface emitting laser omits the complicated process of producing laser mirrors of the edge emitting laser by the cracking and dry etching methods. Furthermore, the vertical-cavity surface emitting laser (VCSEL) has the following advantages:
(1) The low scattered circular laser beam is coupled to the optical fiber easily.
(2) The VCSEL has a high speed modulation function that facilitates high speed optical fiber network transmissions.
(3) The manufacturing process technology of components is suitable for mass production.
(4) Before the epitaxy is cut and packaged, the properties of each crystal grain of the whole wafer are tested by the wafer-lever testing, and thus it incurs a lower cost.
(5) A one-dimensional (1D) or two-dimensional (2D) laser matrix can be produced for facilitating a serial or parallel optical fiber transmission.
The structure of a vertical-cavity surface emitting laser (VCSEL) is generally divided into four types: Etched Air-Post, Ion Implanted, Regrowth Buried Heterostruture, and Oxide Confined, and most commercial products adopt the Ion Implanted type, because its manufacturing process is simple and suitable for mass production. However, when the ion implant technology is used, its implant area cannot be too close to the active layer of the surface emitting laser, otherwise the high-energy particles may destroy the material of the active layer and deteriorate the properties of the laser components, and thus the ion-implant vertical-cavity surface emitting laser (VCSEL) is not suitable for high frequency operations. Therefore, the commercial laser products tend to be developed as oxide confined vertical-cavity surface emitting lasers (VCSEL), whose properties are better than those of the ion implant lasers mainly because its light emitting active area is narrower, and thus obtaining a lower critical current, and a high-quantum efficient and low critical voltage. As to the oxide confined technology, an aluminum gallium arsenide (AlGaAs) with a high aluminum content is introduced adjacent to the active layer and selectively etched to expose it in a high-temperature water vapor, and then the AlGaAs layer with a high aluminum content will be converted into an insulating aluminum oxide dielectric layer to achieve the effect of confining currents and photons. However, its shortcoming resides on that the level of difficulty of the related technology is higher. After a device is selectively etched, the device will have a non-planarized surface which may produce a crack and cause a poor yield rate of the device, when the metal electrode is produced on a non-planarized surface.
To respond to the existing shortcomings of the foregoing oxide confined vertical-cavity surface emitting laser (VCSEL), different manufacturing methods are developed to produce VCSEL, such as those disclosed in U.S. Pat. Publication No. 2003/0123502 (R.O.C. Pat. Publication No. 200306043), U.S. Pat. No. 6,658,040 (R.O.C. Pat. No. 151547), and R.O.C. Pat. No. 192770. These patented technologies mainly adopt a trench oxide confined technology to produce the VCSEL, and thus the requirements for the etching equipments will be higher, and the inductively coupled plasma (ICP) etching system must be used. Of course, the equipments and manufacturing costs will be more expensive. Further, U.S. Pat. Nos. 6,645,848 and 6,570,905, R.O.C. Pat. No. 130588, and R.O.C. Pat. Publication No. 580785 disclosed the methods of producing VCSEL by an oxide confined platform. It is worth to point out that the technical contents related to oxide confined vertical-cavity surface emitting lasers (VCSEL) and disclosed in these prior-art patented technologies adopt the single-platform semiconductor as the basic architecture to build the light emitting active area of the vertical-cavity surface emitting laser (VCSEL).
It is worth to note that U.S. Pat No. 6,645,848 issued to John R. Joseph, et al, U.S. Pat. No. 6,658,040 (R.O.C. Pat. No. 151547) issued to Syn-Yem Hu et al, and U.S. Pat. No. 6,570,905 issued to Karl Joachim Ebeling disclosed the same foregoing methods of using a single-platform semiconductor as the basic architecture to build the light emitting active area of the vertical-cavity surface emitting laser (VCSEL) and further using a dielectric material to fill a metal layer after the light emitting active area is produced, so as to create a wire bonding area electrically coupled to the light emitting active area. However, the wire bonding area created by filling a dielectric material has a weaker mechanical stress due to the properties of the dielectric material. As a result, films often cracks during the wire bonding process, and the effect of the wire bonding will be affected adversely, or even worse, the wire bonding cannot be completed.